Issues calling other xfinity customers

I have been having a lot of xfinity voice issues.  A tech came out and we plugged my main phone into the modem directly as it was deemed the wiring in my house was not good.  Now I have a dial tone again.

NEW PROBLEM:

When I try to make a call from my landline to my mom's landline (which is another xfinity line) the line on my end just rings and rings and rings.  I call her from my cell phone and she answers and stated she picked up the phone and said hello, but all she hears is silence, but on my end I am hearing it ring to infinity. 

So next I tried calling my cell phone from my home phone and it works fine.  It makes a connection.  I call her cell phone from my home phone and it connects.  It only appears to be an issue when  am making an xfinity landline to xfinity landlilne call.

What could be the issue now?